Ribbon cartridges for use with computer printers, typewriters, and the like, are well known in the art. Typically, such cartridges have a housing defining a storage chamber therein for storing an endless ink ribbon in a plurality of loops. The housing includes means for guiding successive portions of the endless ribbon out of the storage chamber, outside of the housing where the ribbon is engaged by the printing mechanism of the printer or typewriter, and back into the housing and to the storage chamber. A drive roller mounted for rotation within the housing engages successive portions of the ribbon to move it along its path, and a pinch roller spring biased against the drive roller is often provided with the ribbon running therebetween to provide for positive engagement of the ribbon by the drive roller.
Typically, the supply of ink with which the ribbon is impregnated will be exhausted long before the ribbon wears out. As the ribbon's supply of ink becomes depleted, print quality becomes increasingly lighter. Finally, the quality of the print becomes so light as to be unacceptable, and the ribbon cartridge must be discarded.
In order to derive further use from the ribbon cartridge, it is known in the art to provide apparatus disposed within the cartridge housing to reink the ribbon. A typical prior art reinking arrangement is shown in U.S. Pat. No. 4,213,705. A porous roller saturated with ink is mounted for rotation within the housing, and a coating roller is mounted for rotation tangentially to the inking roller. The endless loop ribbon is brought into contact with a portion of the coating roller as it is drawn along its path. Ink is transferred from the inking roller to the coating roller and thence to the ribbon so that the ribbon is continuously reinked.
Such arrangements suffer a number of disadvantages, among them being the necessity of additional components separate from those required to transport the ribbon. Not only do these additional components complicate the assembly of the cartridge, but they also present space considerations, since they take up room which could otherwise be used to store additional ribbon in the cartridge, or to reduce the size of the cartridge.
Such considerations become even more important in light of the current trend to downsize printers. As the overall dimensions of the printer are reduced, the space available for the ribbon cartridge is at a premium. Typically, where a standard ribbon cartridge might store forty-five feet of ribbon, the new smaller ribbon cartridges used in compact printers, such as the Okidata 192, include space to store only six feet of ribbon. Thus, while apparatus for reinking this short length of ribbon is necessary to prevent it from having to be replaced 71/2 times more often than a standard ribbon cartridge, the very size constraints that limit the length of the ribbon also limit the amount of space available for a reinking apparatus.
Accordingly, there is a need to provide a reinking apparatus for use in ribbon cartridges which minimizes the number of additional components necessary to accomplish its task.
One design which has sought to provide a compact reinking apparatus requiring a minimum of additional components is embodied in the ribbon cartridge provided as original equipment for the Okidata 182/192 series of printers. This reinking apparatus employs the pinch roller as the coating roller, thereby eliminating the need for a separate coating roller. However, where a separate coating roller can be mounted in a fixed position within the cartridge housing to maintain constant contact with the ink reservoir, a pinch roller is movably mounted within the cartridge housing and spring biased against the drive roller. Thus, apparatus must be provided which maintains contact between the ink reservoir and the movable pinch/coating roller.
The aforementioned Okidata cartridge attempts to solve this problem by employing an ink reservoir including a flexible wick disposed to contact the pinch roller. The wick transfers ink from the reservoir to the pinch roller, and the pinch roller thus reinks the ribbon in addition to maintaining the ribbon in frictional contact with the driven take-up roller. As the pinch roller moves toward or away from the drive roller, the wick flexes to maintain contact therewith. However, this arrangement suffers the disadvantage that a wicking action does not transfer ink to the pinch roller nearly as evenly as a rotating inking roller in actual physical contact with a transfer roller. Uneven ribbon inking results, causing light and dark areas of print known as "hot spots", resulting in print quality which is unacceptable to the end user.
Accordingly, there is a need to provide a ribbon reinking apparatus which maintains constant physical contact with the movable pinch roller while providing an even transfer of ink to the pinch roller.